A conventional universal joint structure is disclosed in TW Patent No. 209513 and contains a holder with a receiving groove and a spherical fitting knob. The fitting knob is pivoted in the holder which has two opposite holes so that an inserting rod is pivoted with the fitting knob, and a spring is fixed in the receiving groove and has a holding piece in which a dented recess is defined. The dented recess is spherical so as to correspond to the spherical fitting knob, and the spherical fitting knob has an orifice for inserting the inserting rod. However, such a conventional universal joint structure has to drill the hole and the orifice thereon and then to insert the inserting rod therein, thus causing troublesome assembly.
Another conventional universal joint structure is disclosed in TW Patent No. M369830 and contains a connecting sleeve with a hole and a coupling shaft. The coupling shaft has an extension formed on one end thereof and inserted into the hole and has a spherical universal joint formed on another end thereof, and between the extension and the universal joint is defined a neck with an outer diameter which decreases. The universal joint has a plurality locking portions evenly arranged therearound and has a fitting sleeve with a retaining recess for connecting with the universal joint of the coupling shaft; a retainer fixed in the retaining recess so as to retain the universal joint. However, the retainer cannot retain the universal joint securely.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.